1. Field of the Invention
The invention relates to safe enclosures which may be installed at locations accessible to customers for vending merchandise, dispensing money or receiving deposits. More particularly the invention relates to sheet metal enclosures which upon attack by an unauthorized force impose one or more additional impediments to an attacker who has only a limited period of time to break into the enclosure before the police or security personnel are able to arrive and intervene against the attacker.
2. Prior Art
Safe enclosures are well known in the prior art, ranging from massive vaults to simple key lock tin boxes. Massive vaults are provided to resist prolonged attack by professional safe crackers and therefore are very thick and heavy. They are unsuited for vending machines because of their mass, bulk and cost. The simple sheet metal enclosures of the prior art, an example of which is the trunk of an automobile, primarily functions to keep amateur thieves from gaining access to the contents. With an inwardly directed force on a sheet metal enclosure, using a punch or other sharp instrument, the sheet metal will deform so that the entire lock mechanism will pop out of its opening to give access to the latch mechanism. With the lock removed, it is often a simple matter to rotate the latch mechanism with a screw driver or other tool and open the sheet metal safe in a matter of seconds.
It is known in the art to provide interengaging elements at the periphery of a door to prevent the door or the side wall from being defined sufficiently to allow the latches to disengage and the door to open. An example is shown in U.S. Pat. No. 3,819,228. It is also known to provide pins or other engaging elements to prevent removal of a door by merely removing the hinges as taught in U.S. Pat. No. 3,970,340.
None of these prior art teachings are effective to protect a sheet metal enclosure following destruction or removal of the lock mechanism.
In U.S. Pat. No. 146,782, auxiliary bolts having no connection to the lock are provided to spring out and fasten the door when a trigger plate over the lock is pressed. This teaching adds significant cost to the enclosure and does not take advantage of deformation of the materials from which the enclosure itself is made.
U.S. Pat. No. 262,103 does show a thick safe door which takes advantage of the deformation which can be expected when an explosive charge, calculated to break or displace the lock mechanism, is detonated against the door. In this patent, the rigidity of the door and the bolt assembly are relied upon to hold the catch and door together to prevent opening the door after damage to the lock. Sheet metal is inherently not rigid and the catch of this patent will not reliably hold in an enclosure made of sheet metal.